In the production of coke in coke ovens from coal substantial amounts of crude gas including ammonia are expelled and are collected in a main collector chamber where the gas is cooled by injection of ammonia water. The ammonia water after rinsing the entire collector chamber then passes, together with substantial amounts of tar separated from the crude gas, into a so-called tar separator. The separation in the tar separator of the tar from the ammonia water is easily accomplished since the tar, because of its higher density forms a lower layer while the ammonia water constitutes the upper layer. The tar and ammonia water are discharged by separate discharge ducts. The ammonia water usually is recycled into the collector chamber while the tar is passed on for further processing.
In recent times preheated coal has been used increasingly as the starting product for producing coke. Unfortunately the preheated coal results in still larger amounts of gases which enclose relatively large amounts of coal dust. As a result there forms in the tar separator a top layer of so-called float tar which principally consists of tar, air bubbles, coal dust and water. This coal tar has a relatively low density and therefore floats on top of the ammonia water. It is principally the coal dust which is responsible for the formation of the frothy float tar.
This rather recent phenomenon has proved to be practically intractible. The float tar cannot simply be united with the bulk of the tar discharged from the lower portion of the tar separator nor can it at reasonable cost be processed separately.
The present invention therefore has the object of providing for a process and apparatus for dealing with this problem, that is, for separating the float tar and converting it in a manner that it can then be processed either separately or together with the bulk of the curde tar discharged from the lower portion of the tar separator.